The Kuiper Belt

The Kuiper Belt is a long-surmised and recently (1992) confirmed outer asteroid belt of rock and ice objects orbiting beyond Neptune. Many astronomers regard Pluto as merely the largest of the Kuiper Belt objects.

Kuiper Belt Objects

Data is adapted from a home page by Dave Jewitt (University of Hawaii), who discovered many of the objects listed. For such distant, faint, and slow-moving objects the data are somewhat provisional and subject to revision. Pluto is included for comparison.
The table shows only the first few discovered; hundreds are now known and active researchers maintain
complete tabulations.

Explanation of Table Contents

Object

Provisional designation of the object: Year of discovery followed by letter-number identifiers. None of these objects have been formally named.

a (AU)

Semi-major axis in astronomical units: 1 AU = 149.6 million km, the distance from the Earth to the Sun. The semi-major axis is half the length of the long axis of the object's orbit, and is its average distance from the Sun.

a (mil km)

Semi-major axis in millions of kilometers.

perh (mil km)

Perihelion (minimum) distance in millions of kilometers.

aph (mil km)

Aphelion (maximum) distance in millions of kilometers.

period yr.

Orbital period in years.

e

Orbital eccentricity.

i (deg)

Inclination in degrees to plane of the ecliptic.

Mag (Mr)

Magnitude at average distance.

Diam. (km)

Diameter in kilometers. Estimated from magnitude and other optical data, hence, only approximate.

Interesting Features

Note the extremely faint magnitudes of all these objects. They are almost at the limit of our ability to detect them.

Note that their orbital inclinations are mostly small. These are objects that accreted like all the planets rather than objects formed somewhere else and then perturbed into their present orbits.

1996TL66 is in a class by itself and, apart from comets, is the most distant object in the Solar System. None of the other objects listed have aphelia beyond 8000 million km.

Object

a (AU)

a (mil km)

perh (mil km)

aph (mil km)

period yr.

e

i (deg)

Mag (Mr)

Diam. (km)

Pluto

39.48

5900

4440

7350

248.02

0.249

17.14

14

2400

1992 QB1

44

6582

6122

7043

292

0.07

2

22.8

283

1993 FW

43.9

6567

6239

6896

291

0.05

8

22.8

286

1993 RO

39.4

5894

4715

7073

247

0.2

4

23.2

139

1993 RP

39.3

5879

5233

6526

246

0.11

3

24.5

96

1993 SB

39.4

5894

4008

7780

247

0.32

2

22.7

188

1993 SC

39.7

5939

4811

7068

250

0.19

5

21.7

319

1994 ES2

45.3

6777

6709

6845

305

0.01

1

24.3

159

1994 EV3

43.1

6448

6190

6706

283

0.04

2

23.3

267

1994 GV9

42.2

6313

6313

6313

274

0

0.1

23.1

264

1994 JQ1

43.3

6478

6478

6478

285

0

4

22.4

382

1994 JR1

39.8

5954

5180

6728

251

0.13

4

22.9

238

1994 JS

42.9

6418

4878

7958

281

0.24

14

22.4

263

1994 JV

39.5

5909

5141

6677

248

0.13

17

22.4

254

1994 TB

39.5

5909

4018

7800

248

0.32

12

21.5

258

1994 TG

42.3

6328

6328

6328

275

0

7

23

232

1994 TG2

42.5

6358

6358

6358

277

0

2

24

141

1994 TH

40.9

6119

6119

6119

262

0

16

23

217

1994 VK8

43.5

6508

6508

6508

287

0

1

22

389

1995 DA2

36.3

5430

4779

6082

219

0.12

7

23

169

1995 DB2

43.5

6508

6052

6963

287

0.07

4

22.5

266

1995 DC2

45.2

6762

6762

6762

304

0

2

22.5

338

1995 GA7

39.5

5909

5200

6618

248

0.12

4

23

202

1995 GY7

41.3

6178

6178

6178

265

0

0.9

23.5

TBD

1995 GJ

42.9

6418

5834

7002

281

0.091

23

22.5

301

1995 HM5

39.5

5909

4846

6973

248

0.18

5

23.1

161

1995 KJ1

43.5

6508

6508

6508

287

0

3

22.5

361

1995 KK1

39.5

5909

4786

7032

248

0.19

9

23

166

1995 FB21

42.43

6348

6348

6348

276

0

1

23.5

169

1995 QY9

39.4

5894

4480

7309

247

0.24

5

21.5

TBD

1995 QZ9

39.8

5954

5001

6907

251

0.16

19.5

22.5

TBD

1995WY2

45.87

6862

6588

7137

311

0.04

1.7

23.4

TBD

1995 YY3

39.24

5870

4591

7150

246

0.218

0.44

23.4

TBD

1996 KV1

43

6433

6175

6690

282

0.04

8.4

22.9

268

1996 KW1

46.6

6971

6971

6971

318

0

6

23.4

281

1996 KX1

39.5

5909

5318

6500

248

0.1

1.5

23.9

131

1996 KY1

39.5

5909

5318

6500

248

0.1

31

23.3

126

1996RQ20

39.4

5894

4244

7545

247

0.28

38

22.6

TBD

1996RR20

42.8

6403

6403

6403

280

0

5

22.8

TBD

1996SZ4

39.4

5894

4598

7191

247

0.22

5

23

TBD

1996TK66

42.5

6358

6358

6358

277

0

5

22

TBD

1996TL66

83.8

12536

5265

19808

767

0.58

24

21

500

1997CQ29

44.4

6642

6177

7107

296

0.07

3

22.5

TBD

Plutinos

A surprising fraction - 40 % - of Kuiper Belt objects have orbital periods close to Pluto's. 246 years is 3/2 of Neptune's period of 164 years and is a stable resonance that allows the object to avoid being perturbed by Neptune. In the asteroid belt, similarly, there are gaps where Jupiter would have 2, 5/2, or 3 times the asteroid's period but a cluster of asteroids where Jupiter has 3/2 the asteroid's period.

Kuiper Belt objects with periods close to Pluto's have been dubbed "Plutinos". A list of known plutinos from the list above follows. Pluto is included for comparison.